Effect of Brewster window placement on polarization, beam quality, and output power in a diode-side-pumped ring...

Ring-cavity laser architectures provide important advantages over conventional linear resonators, including reduced spatial hole burning, improved beam stability, and lower intensity noise. In this work, the effect of Brewster window (BW) placement on the performance of a diode-side-pumped ring-cavity Nd: YAG/KTP green laser is experimentally investigated. Two cavity configurations were implemented, with the BW positioned either in the extended arm (EA) of the ring cavity or directly inside the main ring (MR) cavity. The influence of BW position on the green output power, degree of polarization (DOP), beam quality factor (M²), and spatial beam characteristics was systematically examined. The EA configuration produced higher green output power while maintaining excellent polarization stability, with DOP values between 99.6% and 99.8%. In contrast, the MR-cavity configuration exhibited a more symmetric beam profile, improved spatial mode quality, and slightly lower M² values, indicating enhanced spatial beam uniformity. Beam-profile analysis further revealed that intracavity placement of the Brewster window improves spatial mode stability but introduces additional intracavity losses that reduce the generated output power.These results demonstrate that Brewster window placement plays a critical role in balancing output power, polarization performance, and beam quality in ring-cavity green lasers. The findings provide practical design guidance for optimizing diode-pumped Nd:YAG/KTP laser systems for applications requiring either higher output power or improved spatial beam quality and polarization control.